O desenvolvimento de novos recursos terapêuticos capazes de acelerar o processo de reparo tem proporcionado avanços significativos no tratamento de lesões tendinosas. O objetivo do presente estudo foi analisar a influência da radiação LASER HeNe em cicatrização de tendões. Foi desenvolvido um modelo experimental de lesão de tendão de Aquiles através de um procedimento minimamente invasivo em coelhos adultos. Foram utilizados 40 animais distribuídos em quatro grupos de 10 animais (I, II III IV). No grupo I a lesão do tendão foi unilateral (pata direita) e o tendão lesado não recebeu estímulos com LASER. No grupo II a lesão foi unilateral (pata direita) e o tendão lesado recebeu estímulos com LASER. No grupo III a lesão do tendão foi bilateral e apenas a pata direita foi estimulada com LASER. No grupo IV foi realizada \"Sham Operation\" bilateralmente e apenas o tendão da pata direita recebeu estímulo com LASER. Todos os animais foram tratados com dose a 5 J/cm2 de forma pontual com contato direto durante 8 dias consecutivos, diariamente. Após este período os animais foram sacrificados e os tendões de Aquiles submetidos a ensaios mecânicos de tração em máquina de ensaio mecânico. Foram ensaiados 71 tendões, sendo 09 descartados. Embora não tenhamos observado diferença estatística significante nas comparações feitas entre os grupos, podemos notar que existiu uma tendência apontando que os tendões estimulados com LASER apresentaram resistência menor que os grupos controles. Estes resultados sugerem que o LASER diminuiu a resistência dentro das condições estudadas. Relevância Clínica: O presente trabalho mostra o conceito de que a irradiação LASER pode diminuir a resistência mecânica da cicatrização tendinosa em fases precoces do processo. / The development of new therapeutic resources addressing accelerating the repairing process has proportioned a meaningful advance in the treatment of tendon lesions. The purpose of the present study was to analyse the influence of He-Ne LASER radiation on tendon healing. An experimental model of Achilles tendon lesion was developed through a minimally invasive procedure in adults rabbits. We used 40 animals divided in groups of 10 animals each. In group I the tendon lesion was unilateral (right-paw) and the injured tendon did not receive LASER stimulation. In group II the lesion was unilateral (right-paw) and only, the injured side received LASER stimulation. In group III the tendon lesion was bilateral and only the right-paw was stimulated by LASER. In group IV bilateral sham operation was performed and only the right - paw received LASER stimulation. All the animals were treated with 5 J/cm2 dosis in a punctual way with direct contact for 8 successive days. After this period the animals were killed and the Achilles tendons were submitted to mechanical tests in traction on a mechanical testing machine. Seventy-one tendons were tested and 9 were discarded. No statiscally significant difference was observed in the comparison done between groups, however we could notice a tendency suggesting that the tendons stimulated by LASER presented a lesser mechanical resistance. These results suggest that LASER probably reduces the resistance in the studied conditions. Clinic Relevance: The present study supports the concept that LASER irradiation may induce an attenuation of the mechanical properties of the healing tendon in a very early phasis of the proccess.

Compostos elastoméricos a base de borracha natural (NR) e copolímero de butadieno-estireno (SBR) utilizados na banda de rodagem de pneus são tradicionalmente reticulados com enxofre. O uso de peróxidos e co-agentes na reticulação desses compostos ainda é um desafio a se superar com relação às propriedades viscoelásticas requeridas, de extrema importância para um bom desempenho e vida útil dos pneus. Neste trabalho foi avaliado o uso de peróxidos sem e com co-agentes na reticulação de compostos NR/SBR com o intuito de avaliar a eficiência destes na manutenção das propriedades relevantes em relação a um composto tradicionalmente usado na confecção de banda de rodagem de pneus. Onze formulações com diferentes sistemas de reticulação foram preparadas, sendo uma de referência. Foram avaliadas propriedades físicas como dureza, densidade, tração, resistência ao rasgamento, resiliência, abrasão e DPC, e o comportamento dos compostos de NR/SBR com relação ao inchamento em tolueno. As propriedades dinâmicomecânicas dos compostos NR/SBR foram analisadas por DMA e RPA. Os compostos NR/SBR contendo somente peróxidos não apresentaram propriedades comparáveis ao composto de referência vulcanizado com enxofre. Os compostos contendo os sistemas peróxidos/co-agentes, BIS F 40 A-Retilink T40 (composto 10) e BIS F 40 A-Retilink TA 70 (composto 11) apresentaram os melhores resultados. O composto 10 e o composto de referência (composto 1) apresentaram valores similares de tan d a 60°C e tan d a 0°C (DMA), os quais estão correlacionados às propriedades de resistência ao rolamento e tração no molhado, respectivamente. Os resultados mostraram a possibilidade de uso de certos sistemas peróxido/co-agente em compostos de NR/SBR, em substituição ao sistema com enxofre, sem perda de propriedades, tendo como vantagem a redução de componentes na formulação, redução de tempo de processamento, e consequentemente custo da produção de bandas de rodagem. / Rubber compounds based on natural rubber (NR) and styrene-butadiene rubber (SBR) used on tire tread are traditionally crosslinked with sulfur. The use of peroxides and co-agents in crosslinking of these compounds is still a challenge to be achieved, considering the required viscoelastic properties which are extremely important for a good tire performance and lifetime. In this work it was evaluated the use of peroxide systems with and without co-agents as crosslinking agents for NR/SBR compounds, with the aim of evaluating the efficiency of maintaining the key properties related to the traditionally used in the manufactory of tire tread. Eleven formulations with different systems were prepared, a one as a reference. Physical properties such as hardness, density, tensile strength, tear, resilience, abrasion and compression set and the behavior of NR/SBR compounds in relation of swelling Toluene were evaluated. The dynamic mechanical properties of the NR/SBR cured compounds were analysed by DMA and RPA. The NR/SBR compounds cured with only peroxide had poorer properties when compared to the reference compound vulcanized with sulfur. On the other hand, the compounds cured with proxide/co-agents, BIS F40 plus Retilink T40 (compound 10) or plus T70A (compound 11) showed better results.The compound 10 and the reference compound (compound 1) showed similar results of tan d 60 °C and tan d 0 °C (DMA), which are correlated to rolling resistance and wet traction, respectively. The results demonstrate the possibility of using a peroxide/co-agent as a cure system in NR/SBR compound instead of a sulfur-cured compound for tire tread applications, without the loss of desirable properties, lower processing times and consequently reducing manufacturing costs.

Made available in DSpace on 2014-08-20T13:25:41Z (GMT). No. of bitstreams: 1 TESE_Mauro_Fernando_Ferreira.pdf: 34428971 bytes, checksum: 24ff7e5e9163d78b1220c1bbf56e782c (MD5) Previous issue date: 2008-11-28 / This work had as objective to analyze alternatives to increase the useful life of the ferrules of hoe opener rods of no-till planters, through the addition of covering welding. It was verified the performance of five welding types, being used covered electrodes and tubular wire, over the extremity of the hoe. The tests were executed in franc-sandy soil characterized physically by its texture, plasticity index, density, and water tenor, as well as the resistance to the penetration. The wearing, the horizontal and vertical force were obtained in intervals of 10,5km to the limit of 52,5km. The results indicated that the witness ferrule has lost in the average of the experiment 38,41% of its initial mass when it traveled 52,5km while the other welded ferrules traveled between 61,0km and 108,7km to reach the same mass reductions. It was observed that the vertical and horizontal forces contributed with 11% and 89%, respectively, of the resulting force in the hoe. With the use of the coverings, it was obtained an increase of the area worked in the sowing, for the largest durability of the tools, between 2,0ha and 13,4ha, in relation to the witness. The theoretical field efficiency was larger when it was used the coverings. The tubular wire increased in 5,1% in relation to the ferrule without covering. Starting from the found results we can conclude that it is possible to increase the useful life of the ferrules of furrow opener rods through the addition of welding material and that the conservation of the geometry of the tools, provides the maintenance of the forces that have action on these ones as well as their functional characteristics. / Este trabalho teve como objetivo analisar alternativas para o aumento da vida útil das ponteiras de hastes sulcadoras de semeadoras adubadoras, através da adição de soldagem de revestimento. Verificou-se o desempenho de cinco tipos de soldagem, utilizando-se eletrodos revestidos e arame tubular, sobre a extremidade das ponteiras. Os testes foram executados em solo franco-arenoso caracterizado fisicamente pela sua textura, índice de plasticidade, densidade e teor de água, assim como a resistência à penetração. O desgaste, a força horizontal e vertical foram obtidos em intervalos de 10,5km até o limite de 52,5km. Os resultados indicaram que a ponteira testemunha perdeu na média do experimento 38,41% da sua massa inicial quando percorreu 52,5km enquanto que as demais ponteiras soldadas percorreram entre 61,0km e 108,7km para atingir as mesmas reduções de massa. Observou-se que as forças verticais e horizontais contribuíram com 11% e 89%, respectivamente, da força resultante na ponteira. Com o uso dos revestimentos obteve-se um aumento da área trabalhada na semeadura, pela maior durabilidade das ferramentas, entre 2,0ha e 13,4ha, em relação à testemunha. A eficiência de campo teórica foi maior quando se utilizou os revestimentos sendo que o arame tubular aumentou em 5,1% em relação à ponteira sem revestimento. A partir dos resultados encontrados conclui-se que se pode aumentar a vida útil das ponteiras de hastes sulcadoras através da adição de material soldável e que a conservação da geometria das ferramentas, proporciona a manutenção das forças atuantes sobre estas assim como a suas características funcionais.

Orientador: João Sarmento Pereira Neto / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-09T18:07:40Z (GMT). No. of bitstreams: 1 Tamburus_VivianeSantini_M.pdf: 4949301 bytes, checksum: 97ae79cd54131f23c709101b3e3f8024 (MD5) Previous issue date: 2007 / Resumo: O presente estudo teve o objetivo de investigar o controle vertical do tratamento ortodôntico com AEB cervical, por meio de avaliação cefalométrica, em 26 pacientes dolicofaciais (13 do sexo feminino e 13 do masculino), com maloclusão de Classe II, divisão 1, idade média de 114 meses. O tratamento ortodôntico envolveu a utilização do AEB cervical no arco superior, com 350g de força, por 12-14 horas diárias e arco base no arco inferior até a obtenção da chave de oclusão normal dos molares, e depois foi complementado até a finalização dos casos, segundo a terapia bioprogressiva, com duração média de 56 meses. A avaliação consistiu na análise das seguintes grandezas, em dois momentos, inicial e final do tratamento ortodôntico, as quais foram submetidas à análise estatística pelo teste ¿t¿ de Student: FMA, SN.GoGn, ANB, Fg-S, S-FPm, comprimento maxilar, comprimento mandibular, AFP, AFA, IAF,IMPA, ângulo do plano oclusal, ângulo do plano palatino, QT, LS e ângulo Z. Osresultados mostraram que o tratamento não modificou o padrão de crescimento,ocorrendo estabilidade do plano mandibular (alteração de -1,62º), plano oclusal (alteração de -0,008) e plano palatino (alteração de -0,59º). Ocorreu a correção ânteroposterior das bases apicais verificadas pela redução significativa da grandeza ANB (alteração de -2,61º). A maxila apresentou um suave deslocamento anterior (alteração de 0,57mm) e sua dimensão ântero-posterior aumentou suavemente (alteração de 1,86mm). A mandíbula apresentou melhora de seu posicionamento em relação à base do crânio (alteração de 0,87mm) e sua dimensão ântero-posterior aumentou significativamente (alteração de 9,44mm). As alturas faciais posterior e anterior permaneceram em equilíbrio, não alterando significativamente o IAF. Os incisivos inferiores não apresentaram alterações estatisticamente significantes (alteração de 1,46º). O perfil tegumentar apresentou melhora significativa. O presente trabalho sugere que o tratamento realizado promoveu a correção da maloclusão de Classe II, divisão 1 com controle dos planos horizontais e das alturas faciais, sendo efetivo na estabilidade da dimensão vertical e mostrando-se melhora do perfil / Abstract: The aim of this study was to investigate the vertical control of orthodontic treatment with cervical AEB, by means of cephalometric assessment, in 26 dolicofacial patients (13 girls and 13 boys), with Class II, Division 1 malocclusion, with a mean age of 114 months. Orthodontic treatment involved the use of cervical AEB in the maxillary arch, with 350g of force, for 12-14 hours a day, and the base arch in the mandibular arch until normal molar occlusion was obtained, and afterwards it was complemented until the cases were finalized, in accordance with bioprogressive therapy with a mean duration of 56 months. The assessment consisted of analysis of the following variables, at two moments, the beginning and end of orthodontic treatment, which were submitted to statistical analysis by the Student¿s-t test: FMA, SN.GoGn, ANB, Fg-S, S-FPm, maxillary length, mandibular length, AFP, AFA, IAF, IMPA, angle of the occlusal plane, angle of the palatal plane, QT, LS and angle Z. The results showed that the treatment did not change the growth pattern, with stability occurring in the mandibular plane (alteration of - 1.62º), occlusal plane (alteration of -0.008) and palatal plane (alteration of -0.59º). Antero-posterior correction of the apical bases occurred, verified by the significant reduction in the variable ANB (alteration of -2.61º). The maxilla presented a slight anterior displacement (alteration of 0.57mm) and its antero-posterior dimension increased slightly (alteration of 1.86mm). The mandible presented improvement in its position in relation to the base of the cranium (alteration of 0.87mm) and its anteroposterior dimension increased significantly (alteration of 9.44mm). The posterior and anterior facial heights remained in equilibrium, with IAF not altering significantly. The mandibular incisors presented no statistically significant alterations (alteration of -1.46º). The tegumentary profile presented significant improvement. The present study suggests that the treatment performed corrected the Class II, Division 1 malocclusion, with control of the horizontal planes and facial heights, and was effective for vertical dimension stability, and showing profile enhancement / Mestrado / Ortodontia / Mestre em Radiologia Odontológica

Nas últimas décadas, os avanços na agricultura se destacam principalmente por meio da mecanização e pela eletrônica embarcada, a qual otimizou os processos e viabilizou redução de custos. No entanto, a massa cada vez mais crescente e o intenso tráfego desses equipamentos promovem a compactação do solo, resultando em prejuízos ao setor agrícola. Neste sentido, os objetivos deste de trabalho foi desenvolver sensores que permitam avaliar, as pressões exercidas ao solo decorrentes do tráfego de máquinas e implementos agrícolas e empregá-lo em um estudo para verificar os efeitos da esteira metálica instalada sobre pneus de alta flutuação em ambiente agrícola, bem como a variação na força de tração de acordo com o rodado utilizado. Sendo a hipótese 1 do trabalho, de que esteiras conferem menor pressão sobre solo devido à maior área de contato, resultando em menor compactação e a hipótese 2 de que a utilização das esteiras leva a maior exigência tratória. O desenvolvimento dos sensores e a condução do ensaio foram realizados no campus da ESALQ/USP, as esteiras metálicas foram instaladas sobre os pneus de BPAF de um transbordo de cana-de-açúcar preenchido com solo, para simular uma carga 7500 kg. O ensaio foi dividido em 02 tratamentos (Pneu BPAF e Esteira Metálica), com 04 passadas sucessivas do transbordo carregado sobre os sensores dispostos no solo, na horizontal, vertical e diagonal. Foram determinadas as áreas de contato dos dois tipos de rodado, por meio de imagem digital e mensurada a força de tração exercida pelo transbordo carregado e vazio. Com base nos resultados de pressão exercida ao solo, observou-se uma diminuição de 50% da pressão superficial utilizando esteiras metálicas comparada com os pneus BPAF, em contrapartida a força de tração do transbordo utilizando esteira metálica foi 137% maior. Portando conclui-se que o sensor desenvolvido foi capaz de estimar os picos e as pressões residuais exercidas ao solo em diferentes profundidades e ficaram comprovadas as hipóteses do trabalho. / In recent decades, advances in agriculture are distinguished mainly by mechanization and onboard electronics, which enabled streamlined processes and reduced costs. However, the increasing mass and heavy traffic of these equipments promote soil compaction, resulting significant agricultural losses. This work aimed to develop sensors to assess the stress on soil, resulting from traffic and agricultural machinery and, use them in a study to verify the metal tracks effects installed on high flotation tires on agricultural environment, as well as the variation in traction force according to the used tires. This study considered the following hypothesis: 1. metal tracks give less stress on soil due to greater contact area, resulting in less compaction; 2. the use of metal tracks leads to a greater demand of tractors. The development of sensors and trial conduction were held on ESALQ / USP campus. The metal tracks were installed on the tires of the sugarcane transshipment filled with soil to simulate a load of 7500 kg. The test was divided into 02 treatments (High Floatation Tire and Metal Tracks), with 04 transshipment successive passes loaded on the sensors horizontally, vertically and diagonally placed on soil. The contact areas of the two types of tires were determined through digital imaging and the traction force exerted by loaded and empty transshipment. Considering the stress results on soil, there was a decrease of 50% of the surface stress using metal tracks compared to the tires. However the transshipment traction force using a metal tracks was 137% higher. Therefore, the developed sensor was able to estimate the peaks and the residual stress exerted on soil at different depths and the hypothesis were confirmed.

The agricultural tractor allows to move and to pull machines and implements used during the execution of the activities to field. One of the largest problem refers to the acting of the tractor, the reason of a lot of questions between farmers and manufacturing companies. The perfomance determination is a much complex task, mainly when realized in field level, because the variables that should be analyzed are countless, inside of an extremely wide context. The solution found by a lot of researchers was the standardization through testings realized in concrete track, what shows unreliable results about the perfomance of the tractor in the field, besides they can be expensives. The aim of this work was to previse, through dynamometrics tests, the perfomance of an agricultural tractor of wheels in track and in the field, without appeal to the direct tests. The experiment was conducted in Federal University of Santa Maria, submitting a instrumented tractor to dynamic tests of traction in a paved surface and in the field, besides static tests, using an electric dynamometer with Foucault current. Through the use of equations, already conceptualized, was possible to create a interrelation between the following variables: torque and power of the engine, resistance to the rollover, wheel slipping, relation between the transmission relation and the tires dimensions, providing a way to estimate the power developed in the traction bar and the fuel consumption, with subsequent comparison with the dynamic tests. It was found by the correlation analysis, using obtained and estimated values, that there was a high correlation coefficient between the power traction observed in the track and in the field, relative to the estimated power (0.99 and 0.98) respectively.The equations estimating the fuel consumption presented a high adjustment for 90%, obtaining variation between the field treatments and the track in order to 1,19% and 2,09% respectively. Therefore, the estimate of the tractor performance can be made with high accuracy, just doing the dynamometric tests in laboratory, substituting the dynamic tests of field and track. / O trator agrícola permite movimentar e tracionar máquinas e implementos utilizados durante a realização das atividades a campo. Um dos maiores problemas refere-se ao desempenho do trator, razão de muitos questionamentos entre agricultores e empresas fabricantes. A determinação do desempenho é uma tarefa bastante complexa, principalmente quando realizada em nível de campo, pois inúmeras são as variáveis que devem ser analisadas, dentro de um contexto extremamente amplo. A solução encontrada por inúmeros pesquisadores foi a padronização através de ensaios realizados em pista de concreto, o que remete a resultados pouco precisos referindo-se ao comportamento do trator a campo, além de serem dispendiosos. O objetivo deste trabalho foi prever através de ensaios dinamométricos, o desempenho de um trator agrícola de rodas em pista e a campo, sem recorrer aos ensaios diretos. O experimento foi conduzido na Universidade Federal de Santa Maria, submetendo um trator instrumentado a ensaios dinâmicos de tração em superfície pavimentada e campo, além de ensaios estáticos, utilizando um dinamômetro elétrico de corrente de Foucault. Através do uso de equações, já conceituadas, pôde-se realizar a inter-relação das seguintes variáveis: torque e potência do motor, resistência ao rolamento, patinamento, relação de transmissão e dimensões dos pneus, obtendo-se uma estimativa da potência desenvolvida na barra de tração e consumo de combustível, com posterior comparação aos ensaios dinâmicos. Verificou-se através da análise de correlação, utilizando os valores obtidos e estimados, que houve um elevado coeficiente de correlação entre a potência de tração observada no campo e pista em relação à potência estimada, (0,99 e 0,98) respectivamente. As equações de estimativa do consumo de combustível apresentaram um ajuste superior a 90%, obtendo variação entre os tratamentos de campo e pista na ordem de 1,19% e 2,09% respectivamente. Portanto, a estimativa do desempenho de um trator pode ser feita com elevada exatidão, realizando-se o ensaio dinamométrico em laboratório, substituindo desta forma, os ensaios dinâmicos de campo e pista.

Les travaux effectués dans cette thèse portent sur l'étude du comportement des éléments en béton armé avec de l'acier inoxydable. Le comportement d'une barre d'acier seule n'est pas le même que celui d'une barre enrobée de béton. L'adhérence permet au béton situé entre les fissures de résister à des efforts de traction, réduisant ainsi le niveau moyen d'effort dans l'acier. La considération de cet effet a nécessité la mise en place d'une méthodologie expérimentale et numérique afin de déterminer les paramètres de transfert d'une partie des efforts de traction de l'acier vers le béton. Une nouvelle loi de comportement spécifique pour les barres en acier inoxydable a été développée. Cette loi est intégrée dans une approche de modélisation non linéaire du comportement d'éléments en béton armé selon une discrétisation par couches horizontales pour l'analyse en section et une discrétisation verticale pour l'analyse globale. Cette approche permet de déterminer les paramètres du modèle de raidissement en traction du béton. Ces paramètres sont identifiés grâce à la méthode inverse par comparaison entre les résultats expérimentaux et ceux issus du calcul numérique. La comparaison entre les résultats expérimentaux et la prédiction du modèle implémenté dans Abaqus démontre une très bonne concordance. Enfin, l'effet de l'acier inox sur les réponses structurales sous actions sismiques est présenté. Trois modèles sont conçus et analysés vis-à-vis de la capacité sismique en tenant compte de la ductilité structurale apportée par les armatures inox / This thesis focus on studying the behavior of composite concrete reinforced with inoxydable steel. The behavior of a bare steel bar is not the same as that of a bar embedded in concrete. The grip allows the concrete between cracks to resist tensile forces, thereby reducing the average level of stress in the reinforcement steel bars. The consideration of this effect required an experimental and numerical methodology to determine the parameters that describe the transfer of part of the tensile stress in steel bars to concrete. A new constitutive law has been specifically developed for the inoxydable steel bars. This law is integrated into a nonlinear modeling approach of reinforced concrete elements based on discretization in horizontal layers for the analysis section and a vertical discretization for the overall analysis. This approach is able to determine the tension stiffening parameters of the concrete. These parameters are identified using an inverse method by comparing experimental results and those from the numerical calculation. The comparison between experimental results and the prediction of the model implemented in Abaqus shows a very good correlation. Finally, the effect of inoxydable steel on structural responses under seismic actions is presented. Three models are designed and analyzed based on the seismic capacity taking into account the structural ductility of the inoxydable steel

Les protéines fibreuses (kératine, élastine, collagène, fibroïne…) représentent 1/3 des protéinesconstitutives des mammifères et des oiseaux. Ce sont des protéines qui ont une fonction de protection et/oumécanique. La soie apparait comme le système le plus « simple » car elle est principalement constituée demotifs de répétition à base d’alanine et de glycine, deux petits acides aminés. Certaines soies présentent despropriétés mécaniques comparables ou supérieures à celles des fibres synthétiques et seraient susceptiblesd’être de nouveau largement utilisées dans des applications techniques (par exemple biomédicales) si lavariabilité de leurs propriétés était maîtrisée. Ce travail porte sur la structure des soies grèges ou décreuséesde Bombyx mori (ver à soie domestique), de Nephila madagascariensis (araignée sauvage, fibre sansenveloppe de séricine), de Bombyx mori génétiquement modifié (incluant un gène de Nephila) et sur unesoie recombinante 4RepCT (Escherichia coli). La soie est analysée par spectrométrie Raman (et IRTF) ettraction uni-axiale, ainsi que par le couplage de ces méthodes. L’analyse de la région des bas nombresd’onde en spectroscopie Raman a permis de caractériser des régions ordonnées de 2 à 3 μm de long etdistantes d’environ 60 μm. Il s’agit de la première mise en évidence d’une hétérogénéité de structure de lasoie. Le couplage avec la traction uni-axiale montre une sollicitation de ces régions ordonnées sousdéformation, suggérant une organisation de la soie selon le modèle de Prevorsek, c’est à dire qu’une mêmechaîne macromoléculaire appartient à la fois à des régions amorphes et à des régions ordonnées. L’étudestatistique des propriétés mécaniques de la soie de ver et d’araignée montre une grande distribution, maisune bonne stabilité dans le temps (dizaines d’années). La modification génétique ne procure pasd’amélioration des propriétés mécaniques de la fibre, seulement une légère diminution de la variabilité.Diverses stratégies sont mises en oeuvre pour tenter d’échapper à cette variabilité : production bactérienne,solubilisation de la soie et régénération sous forme de films. Le rôle de l’eau lors de la biosynthèse de lasoie, ainsi que l’effet de divers paramètres (filtration, pH, séchage…) lors de la préparation des films ont étéétudiés. Nous avons pu confirmer que la présence d’agrégats de protéines favorise l’organisation dans lesfilms et 2 types de films ont donc été préparés. Les films les plus amorphes présentent les propriétésmécaniques les plus intéressantes, même si elles n’atteignent de quelques % de celles des fibres. Lafabrication de composites à matrice de soie régénérée renforcée par des fibres de soie permet d’augmenterla résistance et la déformation à rupture. Ces premiers résultats sont encourageants pour le développementde matériaux composites fibres de soie/matrice de soie régénérée. / Fibrous proteins (keratin, elastin, collagen, fibroin ...) make up to one third of the proteins ofmammals and birds. They are structural proteins with a protective and/or mechanical function. Silk appearsto be the ‘simplest’ model because it mainly consists of two small amino acids residues (alanine andglycine). Some silks have comparable or superior mechanical properties compared to those of syntheticfibres and could be used in technical applications (e.g. biomedical) if the variability of their properties canbe controlled. This work focuses on the structure of silks from: Bombyx mori (domestic silkworm)degummed or not, Nephila madagascariensis (wild spider, no sericin coating), GM Bombyx mori (includinga gene of Nephila) a recombinant spider silk 4RepCT (Escherichia Coli). Silk is analyzed by Ramanspectroscopy (and FTIR), uni-axial tensile testing, and also by the coupling of these methods. The analysisof the low wavenumbers region in Raman spectroscopy allowed the characterization of ordered regions of 2to 3 microns separated by about 60 microns. This is the first evidence of the heterogeneous structure ofsilk. Coupling with the uni-axial tensile test shows that these ordered regions are stressed under macroscopicdeformation, suggesting silk organization according to Prevorsek’s model, i.e. that the samemacromolecular chain belongs to both amorphous and ordered regions. The statistical study of themechanical properties of silkworm and spider silks shows great dispersion, but a good stability over time(decades). Genetic modification does not improve the fibres mechanical properties but a slight decrease intheir variability. Various strategies have been investigated to control the variability: bacterial production,solubilization of silk and films regeneration. The role of water in silk biosynthesis, as well as the effect ofvarious parameters (filtration, pH, drying ...) during the preparation of the films were studied. It wasconfirmed that the presence of protein aggregates promotes the organization in film and two types of filmswere prepared. The most amorphous ones have the most interesting mechanical properties, though only afew percent of those from the starting fibres. The fabrication of regenerated silk matrix compositesreinforced by silk fibres increases the strength and strain to failure. These initial results are encouraging forthe development of silk fibres/regenerated silk matrix composite materials.

L’étude réalisée dans le cadre de cette thèse représente une recherche sur la durabilité de la réparation par collage de patchs externes de structures composites endommagées. Le comportement des réparations sollicitées en traction a été étudié. Les approches expérimentale et numérique ont été réalisées. La qualité et la répétitivité des réparations dépendent fortement du savoir-faire employé durant leur mise en œuvre. A ce titre, un protocole de fabrication précis a été établi et validé. Ce protocole a ensuite été appliqué strictement dans l’ensemble de l’étude. L’effet de la géométrie des patchs sur la performance des réparations en traction a été discuté. De plus, deux séries de patchs présentant des rigidités de membranes et des séquences d’empilement différentes ont été testées. Pratiquement, plusieurs méthodes de contrôle ont été appliquées pour localiser l’initiation de l’endommagement et suivre son évolution jusqu’à la rupture final. L’observation des scénarios d’évolution de l’endommagement a conduit à proposer trois modèles phénoménologiques permettant l’élaboration et la validation d’un modèle numérique.Le modèle numérique proposé a été validé grâce à la corrélation avec les résultats expérimentaux. Ensuite, ce modèle a été appliqué pour réaliser une étude paramétrique. Les résultats obtenus ont permis de proposer un modèle d’aide à la conception et à l’optimisation des structures composites réparées. Ce modèle fournit des informations intéressantes sur la meilleure combinaison des paramètres de réparation à utiliser. / The study in this thesis represents research on the durability of the repair of damaged composite structures by bonding external patches. The behaviour of the remedies sought in tension was investigated. The experimental and numerical approaches have been made.The quality and repeatability of repairs depends heavily on skills used during their installation works. As such, a specific manufacturing protocol was established and validated. This protocol was then applied strictly throughout the study. The effect of patch geometry on the performance of repair in tension has been discussed. In addition, two sets of patches with the different membrane stiffness and stacking sequences were tested. Practically, several control methods were applied to locate damage initiation and follow its evolution until the final rupture. Observing damage evolution scenarios has led to propose three phenomenological models for the development and validation of a numerical model.The proposed numerical model has been validated through correlation with experimental results. Then, this model was applied to perform a parametric study. The results obtained allowed to propose a model to help design and optimization of repaired composite structures. This model provides interesting information on the best combination of repair settings.

Most farming at subsistence level is located in rural areas where the majority of smallholder farmers have low productivity which results in high rate of food insecurity. The areas are characterised by animal traction and poor farming practises, and monoculture is mostly preferred. In light of this, this study analyzed the impact of animal power on agricultural productivity. Smallholder farmers in the lowlands of Mohale’s Hoek district of Lesotho were investigated by means of a case study methodology. The aim of the study was to inform agricultural policy about the level and key determinants of inefficiency in the smallholder farming system so as to contribute to policy designed to raise productivity of smallholder farmers. The sampling frame comprised farmers and extension workers in the lowlands of Mohale’s Hoek district. From this frame, 118 farmers and 4 extension workers were randomly selected from four villages, namely‘Mapotsane, Potsane, Tsoloane and Siloe. The four groups of farmers include; the farmers owning and using cattle for ploughing, farmers owning tractor and cattle and using them for ploughing, farmers owning tractor only and using it for ploughing, and farmers who owned neither cattle nor tractor and normally hire these when ploughing operations are to be done on the farm. The interviews of these farmers and extension workers were conducted by means of semi-structured questionnaire which consisted of both open and close ended questions. The study used the stochastic frontier production model for the production efficiencies and linear regression model for the impact of animal traction on agricultural productivity. Both procedures provided insights into the relative contributions of animal power and traditional systems to poverty alleviation and food security in the project areas. Descriptive statistics were employed for farming systems and challenges facing small scale farmers. Gross Margins analysis was conducted for the animal power and tractor power yield levels for maize crop to compare the two types of power. Some diagnostic tests to detect serial correlation and heteroskedasticity and t-tests were also performed. The significant variables include the area of sorghum ploughed, members of the household that assist with family labour, education, quantity of fertilizer applied, time taken by the farmers in farming, members who are formally employed, household size, area of land ploughed, old age, costs of tractor and animal, marital status, income, area of maize ploughed, area of sorghum ploughed, quantity of fertilizers applied, costs of seeds and fertilizers applied, maize and sorghum yield and amount sold and consumed. The study revealed that monoculture is mainly practised and many smallholder farmers used traditional technologies that fail to replace nutrients in the soil. Nonetheless family labour was not a problem. During the farming season, tractors were used as the main source of power for ploughing. Most farmers hired these for maize production as it is a staple food crop even where animal power is available. It was noted that the tractors were few and in most cases old and malfunctioning. The cost of using animals in farming obviouslyplayed a role in the production of both maize v and sorghum in the lowland areas of Mohale’s Hoek district. Smallholder farmers who owned both tractors and animals produced more but they were mainly affected by high costs of maintaining the aging tractors, generally purchased on the used-equipment market. The increased challenges resulted in lower productivity of the smallholder farmers, including: unhealthy animals, drought, marketing problems, late ploughing, poor soils, lack of extension services, low yields, low income, lack of information, lack of appropriate implements, lack of support services, nutrition inadequacy, inappropriate farming systems. The study recommended the adoption and promotion of low-cost mechanization in the lowlands of Mohale’s Hoek district so as to increase the production of the smallholder farmers. Increased productivity will in turn improve household food security.